Effect of γ-irradiation on the gauge factor of two-dimensional island platinum films

Abstract

Four films (A, B, C and D) of two-dimensional island platinum films (2D-I(Pt)Fs) whose mass thicknesses (dm) are 10, 20, 30 and 40Å, respectively were deposited onto Corning 7059 glass substrates via the thermal evaporation technique. The increase in the film resistance with time (aging) in air is monitored until stable values are obtained. Each of the prepared films was γ-irradiated by different doses, namely, 100, 200, 300, 500 and 700Gy; this was done using 137Cs (0.662MeV) radiation source of dose rate 0.5Gy/min. For each dose the relative change in the film resistance was found at different values of strain either in the tensional or compressional mode. The gauge factor (v) of the Pt films was deduced and we found that; for particular dm, the gauge factor decreases as the dose increases. Also, for a particular dose, v decreases as dm increases. Qualitative interpretation for the results was offered on the ground that (i) the transfer of electrons between islands takes place by the thermally activated tunneling mechanism, (ii) the process of γ-irradiation makes the islands spread along the substrate and consequently the inter-island spacing will decrease. The micrographs taken by the Atomic Force Microscope (AFM) confirmed such spreading.